Volumes of brain structures in captive wild-type and laboratory rats: 7T magnetic resonance in vivo automatic atlas-based study

Abstract

Selective breeding of laboratory rats resulted in changes of their behavior. Concomitantly, the albino strains developed vision related pathologies. These alterations certainly occurred on the background of modifications in brain morphology. The aim of the study was to assess and compare volumes of major structures in brains of wild-captive, laboratory albino and laboratory pigmented rats. High resolution T2-weighted images of brains of adult male Warsaw Wild Captive Pisula-Stryjek rats (WWCPS, a model of wild type), laboratory pigmented (Brown Norway strain, BN) and albino rats (Wistar strain, WI) were obtained with a 7T small animal-dedicated magnetic resonance tomograph. Volume quantification of whole brains and 50 brain structures within each brain were performed with the digital Schwarz rat brain atlas and a custom-made MATLAB/SPM8 scripts. Brain volumes were scaled to body mass, whereas volumes of brain structures were normalized to individual brain volumes. Normalized brain volume was similar in WWCPS and BN, but lower in WI. Normalized neocortex volume was smaller in both laboratory strains than in WWCPS and the visual cortex was smaller in albino WI rats than in WWCPS and BN. Relative volumes of phylogenetically older structures, such as hippocampus, amygdala, nucleus accumbens and olfactory nuclei, also displayed certain strain-related differences. The present data shows that selective breeding of laboratory rats markedly affected brain morphology, the neocortex being most significantly altered. In particular, albino rats display reduced volume of the visual cortex, possibly related to retinal degeneration and the development of blindness.

An MRI-Derived Neuroanatomical Atlas of the Fischer 344 Rat Brain

“…Even within-strain differences can be seen by comparing two studies citing whole brain volumes of Wistar rats: although the MRI template set provided by Valdéz-Hernández et al7 was created using Wistar rats of a similar age and weight range to those studied by Welniak-Kaminska et al, Valdéz-Hernández et al cites a whole brain volume of 1764.92 ± 85.57 mm 3 , compared to 1971±22.7 mm 3 quoted by Welniak-Kaminska, which is outside the 10% difference in volume guidelines stated previously. For comparison, the whole brain volume of Fischer rats in this study is 1925±106.80 mm 3 , which is within 10% of the whole brain volumes quoted in other strains of similar age and body weight 7,42. It is still possible that neuroanatomical differences exist between the Fischer 344 strain and other inbred (Lewis, Brown Norway) or outbred (Wistar, Sprague-Dawley, Long-Evans) strains that would cause co-registration between experimental scans to the Fischer atlas to fail.…”

“…2,16,35,42 That said, volume differences in both whole brain and specific structures have been shown between rat strains. 42 • All rats used for this study were four months of age and are therefore considered to have reached mature adulthood. However, due to normal changes in brain shape and volume during the rat lifespan, this atlas may not be applicable to significantly older or younger rats.…”

“…Finally, regarding the generalizability of this Fischer 344 atlas to other rat strains, many studies have successfully applied atlases generated from strains differing from their experimental rats, likely in part due to the lack of an appropriate MRI atlas for their own rat strain and/or research question. 16,42,43,44 In the literature, the general consensus appears to be that any particular atlas, including that designed by Paxinos and Watson, may be applied to both sexes, different strains, etc., provided there are no gross anatomical abnormalities, the age and weight range of the subjects is comparable, and volumes should be within 10% of the template image volume. 2,16,35,42 That said, volume differences in both whole brain and specific structures have been shown between rat strains.…”

“…16,42,43,44 In the literature, the general consensus appears to be that any particular atlas, including that designed by Paxinos and Watson, may be applied to both sexes, different strains, etc., provided there are no gross anatomical abnormalities, the age and weight range of the subjects is comparable, and volumes should be within 10% of the template image volume. 2,16,35,42 That said, volume differences in both whole brain and specific structures have been shown between rat strains. 42 • All rats used for this study were four months of age and are therefore considered to have reached mature adulthood.…”

Validation of chronic restraint stress model in rats for the study of depression using longitudinal multimodal MR imaging

“…Residuals from the model were normally distributed. Hippocampal volume was normalised to the wholebrain volume (% whole brain volume) to adjust for differences in head size (Welniak-Kaminska et al, 2019). Pearson's correlation method was used to determine correlation between baseline percentage hippocampal volume and post-restraint latency to first immobility behaviour during FST.…”